In a number of medical circumstances including routine surgery and intensive care, spontaneous respiratory capability is diminished, and a breathing assist is required. This breathing assist involves the forcing of air into the lungs by positive pressure. Positive pressure ventilation is supplied by a small bag of air or oxygen mixture squeezed by an anesthesiologist or by a bellows or piston in a mechanical ventilator. To insure that the air actually goes into the lungs rather than the esophagus and stomach and to insure that an open airway is always present during surgery or mechanical ventilation in the intensive care unit, a tube is inserted into the trachea such that the distal tip is well below the vocal cords. This tube, called an endotracheal tube, may be inserted through the mouth or the nose but must bend anteriorly in the throat in order to enter the trachea and avoid the esophagus. Once the tube is in place in the trachea, a circumferential balloon-cuff above the distal tip of the endotracheal tube is inflated with air. This balloon-cuff seals the tube in the trachea by filling the area between the tracheal wall and the endotracheal tube. Such an arrangement allows positive pressure to be applied and the lungs inflated by the anesthesiologist or mechanical ventilator. The balloon-cuff also protects the trachea from any foreign material from the mouth or regurgitated from the stomach.
Ever since the endotracheal tubes were introduced, anesthesiologists and other physicians have experienced difficulties placing endotracheal tubes into the trachea, a procedure called intubation. Of all procedures done in the intensive care unit related to maintaining ventilation of critically ill patients, intubation of the trachea is associated with the greatest number of complications. Very few physicians other than anesthesiologists have any proficiency at inserting endotracheal tubes. Usually, intubation involves the use of a device called a laryngoscope.
In order to insure that the endotracheal tube goes into the airway to trachea instead of the esophagus, the anesthesiologist must visualize the vocal cords by extending the patients head slightly and by elevating the jaw of the patient with the laryngoscope. In his position behind the patient's head, he can place the tube between the vocal cords, into the trachea below. One of the principle dangers of this procedure is that it almost always requires that the patient be temporarily paralyzed. Paralysis of the patient facilitates visualization of the vocal cords by relaxing the jaw muscles and preventing the patient from retching or otherwise interfering with the placement of a large piece of metal (the laryngoscope) down his throat. Unfortunately it also eliminates any contribution that the patient might take towards his own breathing. Failure to place the endotracheal tube rapidly can result in death if the patient cannot be ventilated by a mask placed tightly over his mouth and nose in between attempts to intubate with the laryngoscope. Ventilating a patient by mask and positive pressure from a bag of oxygen also requires particular skill and practice and is nearly impossible with some patients and without proper equipment.
Even experienced anesthesiologists have difficulty intubating certain patients. Patients with the following problems are particularly difficult to intubate:
(1) short muscular neck PA1 (2) receding jaw PA1 (3) large, thickened tongue PA1 (4) high arched palate PA1 (5) cleft lip or palate PA1 (6) cervical or temperomandibular arthritis (common in elderly patients, prevents adequate extention of the neck in order to see the vocal cords) PA1 (7) post surgical scars or burns to the face, neck, or mouth PA1 (8) pharngeal or laryngeal tumors PA1 (9) inflammation of the epiglottis or tonsils PA1 (10) facial fractures PA1 (11) thyroid disease (colloid, goiter, substernal thyroid) PA1 (12) deviation of the epiglottis, vocal cords, or trachea from the midline by stricture or kyphoscoliosis.
Such patients are difficult to intubate under the best of circumstances, that is, in the operating room prior to elective surgery. At this time the anesthesiologist has time and appropriate equipment and other skilled persons to give the patient 100% oxygen prior to putting him to sleep and paralyzing him. The patient can be properly positioned and counseled to know what to expect. Even if his intubation is prolonged and difficult, he is put to sleep first by intravenous medication and is not aware of the complication. Intubating patients in the intensive care unit, emergency room, coronary care unit, or elsewhere outside the operating room is much more difficult. Unlike the well-prepared, sedated, and pre-oxygenated patient on the operating room table, the intensive care patient or emergency room patient is often in great respiratory and cardiovascular distress at the time endotracheal intubation is mandatory. He may be so short of breath that he refuses to lie down or allow a tight fitting mask on his face. Time and skill are of great importance, as is experience obviously, to overcome unexpected anatomic problems in choking, suffocating, uncooperative, frightened patients. Some types of lung disease leave the lungs so stiff that adequate ventilation with a mask is not possible. Since the patient is already in respiratory distress despite the usual administration of oxygen by a loosely fitted mask, the rapid institution of an intravenous sedative and paralyzer is a gamble that an endotracheal tube can be inserted swiftly in spite of unexpected anatomical problems which could interfere with intubation, and should intubation not be successful, that an appropriate mask, oxygen source, anesthesia bag, and skill are at hand to ventilate the paralyzed patient in between intubation attempts or until more skilled persons and/or equipment are available. Should the endotracheal tube be inadvertently placed in the esophagus, the forcing of air into the esophagus can result in rupture of the stomach or, more commonly, the inducement of vomiting. Gastric contents may then go into the airway and severely damage the lungs.
Skill with a laryngoscope only comes with constant practice. It is therefore not surprising that only anesthesiologists and certain intensive care physicians are capable of intubating the trachea proficiently. On occasion, an endotracheal tube can be inserted into the nose and blindly advanced into the throat and through the vocal cords without paralyzing the patient. This technique is particularly useful in the patient with acute respiratory distress because it requires only local anesthesia to the nose and allows the patient to continue with his own breathing, although it is not totally adequate for him, during the insertion of the endotracheal tube. Obviously, this blind technique requires even more skill and practice to avoid inserting the tube into the esophagus or injuring the patient. In addition, this nasal approach is often impossible for anatomic reasons even if an experienced person is making the attempt.
These problems have been discussed in part and a proposed device disclosed in U.S. Pat. No. 4,063,561 issued Dec. 20, 1977. The device disclosed therein is a newly constructed endotracheal tube which includes therein metallic material within the walls of the tube and which may be affected by external magnetic devices placed over the larynx of the patient externally. Obviously, the cost of manufacturing individual tubes with metallic wire in the walls would be much greater than the cost of manufacturing the present invention, which can be used with any existing endotracheal tube, is reusable indefinitely, and has no expensive parts.
The above mentioned patent further discloses a possibility of enclosing frictionally a metallic block within the tube lumen which is secured to the end of a flexible wire whereby an ordinary endotracheal tube can be inserted into the throat and the entire tube manipulated by an external magnet into the trachea. All endotracheal tubes must be stiff enough to prevent excessive collapse when they bend. For this reason, normal endotracheal tubes cannot be manipulated externally with a necessarily small piece of metal within the lumen of the tube. Such an arrangement could be potentially dangerous. The block of metal could become dislodged from the wire and drop into the trachea. Further, such a metallic plug may become stuck upon its withdrawal at the point of anterior bend of the endotracheal tube in the nose or mouth, completely occluding the airway. The problems arising from this arrangement are further apparent from the fact that the emphasis in the above mentioned patent is upon the creation of a new endotracheal tube. The attraction of a magnet, no matter how large, for a piece of metal is still a function of the mass of both pieces of metal. The size of the metallic plug as illustrated in the patent cannot be large enough to manipulate a normal endotracheal tube because it must fit into the lumen of the tube. Increasing the size of the magnet outside will not overcome the distances involved or the stiffness of the ordinary tube.
The above disadvantages are overcome by the present invention wherein a very flexible stylet, instead of a whole endotracheal tube, is controlled by an external magnet by incorporating a second magnet into the distal end of the stylet. This small magnet on the distal tip of the stylet has opposite polarity to the external magnet, thus increasing their attraction and providing consistant alignment and direction toward the vocal cords. The stylet may be inserted through the mouth or nose in almost any body position and is of a dimension of fit within a standard endotracheal tube without completely occluding its lumen. After the distal tip of the stylet is within the trachea, the endotracheal tube is advanced over the stylet into the trachea, and the stylet quickly removed. Accordingly, it can be seen that the stylet acts as a flexible intubating guide for the endotracheal tube. To facilitate removal of the stylet from the endotracheal tube, the diameter of the stylet is much smaller than the lumen of the endotracheal tube. The magnet at the tip of the stylet may be constructed out of many small magnets. When stuck together, they function exactly like one long magnet, but when bent around a tight turn will articulate with one another and allow flexibility and easy withdrawal once the endotracheal tube has been advanced over the stylet into the trachea. This arrangement of many small articulating magnets functioning as one magnet is especially useful as the size of the endotracheal tube decreases. Larger endotracheal tubes do not require the articulation of small magnets at the distal tip of the stylet because there is adequate space in the lumen to withdraw the stylet without the magnet becoming lodged in the tube at its point of bend in the posterior pharynx. The flexible stylet may be inserted originally into the mouth or nose and directed into the trachea before the endotracheal tube is advanced over it, or the stylet and endotracheal tube may be advanced as a unit or alternately, as long as the stylet stays several inches in front of the tip of the endotracheal tube. In any case, once the tube has been advanced into the trachea, the stylet is quickly removed, the balloon-cuff of the tube inflated, and positive pressure ventilation initiated. Paralysis is never necessary. Local anesthetic agents may be sprayed or applied to the nose, throat, and tongue prior to insertion of the stylet. Mild sedation may be given, but the patient continues to breathe for himself and may remain in the sitting position if he desires.
Besides a system of nasal or oral tracheal intubation, the stylet is constructed to be not only very flexible and responsive to the external magnet but also to be at least twice the length of a standard endotracheal tube. This extra length provides the ability to change one endotracheal tube that may be defective or too small with a new endotracheal tube, again without paralysis or a laryngoscope. In this case the stylet is inserted (using the end opposite the magnetic tip) into the old endotracheal tube and the old tube removed when the stylet is in the trachea. Then a new tube can be advanced over the stylet and the stylet withdrawn. This procedure is rapid, does not require an external magnet, and is far safer and easier than removing the old tube and necessitating the insertion of a new tube by sedation, paralysis, and a laryngoscope. The stylet is constructed of a material which is spring-like and slides easily inside the endotracheal tube, bends easily but can be pushed, confers enough rigidity to allow guidance for an endotracheal tube, but is very responsive in a magnetic field.
Accordingly, it is the purpose of this invention to provide an endotracheal tube insertion system which does not require the risky technique of paralysis, can be used by anesthesiologists to intubate patients with difficult anatomical problems through the nose or mouth, can be used by relatively unskilled medical personnel in emergencies when an anesthesiologist is not present, can be used in a variety of positions, including supine, sitting and lateral decubitus, and can be used and reused indefinitely on standard endotracheal tubes. This endotracheal tube insertion system provides for a flexible stylet, having a magnet attached to one end, to be guided into the trachea by means of an external magnet with opposite polarity. The endotracheal tube is advanced over the stylet so as to enter the trachea with the subsequent removal of the stylet.
It is a further object of this invention to provide a stylet guiding means which may be used to quickly replace one endotracheal tube for another without paralysis or the use of a laryngoscope.